Heteropaternal superfecundation

Heteropaternal superfecundation is a rarely occurring medical condition, the term describing the fertilization of two or more ovary by sperm from different males. According to Academic Dictionaries & Encyclopedias, "A woman who has sexual relations with two or more men at short intervals within the same ovulatory period can be impregnated by both men," thus twin newborn children are half-brothers or half-sisters with different fathers. Among some animal species, however, it is quite common(such as cats). [1]